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991. Broken Calculator

題目​

完整題目

There is a broken calculator that has the integer startValue on its display initially. In one operation, you can:

  • multiply the number on display by 2, or
  • subtract 1 from the number on display.

Given two integers startValue and target, return the minimum number of operations needed to display target on the calculator.

Example 1

Input: startValue = 2, target = 3
Output: 2
Explanation: Use double operation and then decrement operation {2 -> 4 -> 3}.

Example 2

Input: startValue = 5, target = 8
Output: 2
Explanation: Use decrement and then double {5 -> 4 -> 8}.

Example 3

Input: startValue = 3, target = 10
Output: 3
Explanation: Use double, decrement and double {3 -> 6 -> 5 -> 10}.

在只有乘 2 和減 1 的狀況，找出起始值變成目標值最少步驟次數。

題目難易度​

Medium

解題想法​

初試​

Runtime: 72ms

Memory Usage: 41.7MB

/**
 * @param {number} startValue
 * @param {number} target
 * @return {number}
 */
var brokenCalc = function (startValue, target) {
  let time = 0;

  while (startValue < target) {
    if (target % 2 === 0) {
      target = target / 2;
    } else {
      target++;
    }
    time++;
  }
  return time + startValue - target;
};